This review describes the current methods for exploiting and applying plant growth-promoting rhizbacteria (PGPR), elicitors and semiochemical products in contemporary agricultural systems. The future of ... [more ▼]

This review describes the current methods for exploiting and applying plant growth-promoting rhizbacteria (PGPR), elicitors and semiochemical products in contemporary agricultural systems. The future of these biostimulant and biocontrol tools for the sustainable management of agricultural practices is also discussed. Special attention is given to the formulation of these products and the network of interactions taking place in cultivated ecosystems [less ▲]

Chemical signals are involved in the courtship behavior of many invertebrate and vertebrate species. Lady beetles are no exception to this rule; a significant number of published reports highlight the ... [more ▼]

Chemical signals are involved in the courtship behavior of many invertebrate and vertebrate species. Lady beetles are no exception to this rule; a significant number of published reports highlight the role of cuticular chemicals involved in the reproduction of lady beetles, including gender recognition. Recent data have also demonstrated the presence of a volatile female sex pheromone that facilitates male attraction in some species. Here, we present a synthetic overview of the current knowledge about the sexual behavior of lady beetles and associated chemicals for which the function and identification have been provided. Because lady beetles are often reared as biological control agents, the chemical cues involved in their sexual behavior could be used as components in integrated management approaches against soft-bodied hemipterans. In conclusion, this review provides new perspectives and potential developments for sustainable insect management mainly based on the semiochemicals involved in the sexual behavior of lady beetles. A better understanding of these chemical signals would help maximize their presence in areas where their predatory behavior is requested, as a result of the application of formulations inducing behavioral manipulation. [less ▲]

Sustainable agriculture relies on the development of environmentally friendly methods of crop production. Therefore, alternative solutions are required to decrease insecticide use and to promote the ... [more ▼]

Sustainable agriculture relies on the development of environmentally friendly methods of crop production. Therefore, alternative solutions are required to decrease insecticide use and to promote the efficacy of natural enemies against insect pests. Investigating the sexual behavior of lady beetles is of practical relevance, because these insects could be used to reduce plant-feeding insect populations in crop fields by taking advantage of their predatory behavior. In this context, the objective of this PhD thesis was twofold: (1) a fundamental research that focuses on the identification of the sex pheromone of Harmonia axyridis (Pallas) and (2) an applied approach aimed at elaborating semiochemicals slow-release dispensers with these compounds, in order to attract individuals in cultivated fields. We have demonstrated that virgin females of H. axyridis display a typical male-calling behavior in presence of prey, which is associated with the release of a pheromonal blend that is highly attractive for conspecific males. Dynamic headspace sampling and subsequent chemical analyses allowed the characterization of this sex pheromone. Finally, we focused on the development of a formulation releasing a combination of semiochemicals that attract aphid predators. The formulation, composed of alginate beads, was optimized under laboratory conditions. The release rate of the formulation was assessed by dynamic headspace sampling coupled with adsorbent trapping. The formulation was efficient at attracting two natural enemies of aphids. All these results are discussed in the context of sustainable agriculture, with the use of semiochemicals, and especially pheromones, as potential tools to enhance current cropping systems. In near future, the application of such molecules, based on strong knowledge of insect olfaction, is expected to increase considerably with the development of new methods aimed at attracting predators and/or parasitoids. In addition, improvements of experimental devices, such as the elaboration of slow release dispensers, are suggested in the last chapter of this PhD thesis. [less ▲]

Aphids are important pests of wheat and pea. Among the alternative methods to control them with less reliance on insecticides, crop associations already proved to be efficient. However, if increasing the ... [more ▼]

Aphids are important pests of wheat and pea. Among the alternative methods to control them with less reliance on insecticides, crop associations already proved to be efficient. However, if increasing the chemical and structural complexity of vegetation can disrupt their host plants location, the searching efficiency of predators and parasitoids can also be reduced. Therefore, these beneficials may not always be more abundant in such systems. Combining crop associations with attractive semiochemicals for natural enemies can be interesting to solve this problem. In this research, we compared the effect of a wheat and pea pure stand, wheat and pea mixture, and wheat and pea mixture combined with methyl salicylate (MeSA) formulated in alginate gel beads, on the abundance and diversity of aphids and their natural enemies. These were weekly observed on plants during 2013 and 2014 growing seasons. Over these two years, significantly higher numbers of pea aphids (Acyrthosiphon pisum (H.)) were observed in the pure stand of pea compared with both mixtures (with and without MeSA). No significant differences were observed between treatments for wheat aphids (Sitobion avenae (F.), Metopolophium dirhodum (W.) and Rhopalosiphum padi (L.)), which were significantly less abundant than pea aphids. Aphid natural enemies were mainly observed on pea plants. Hoverfly larvae abundance was not significantly different between treatments during both years. The same phenomenon occurred with hoverfly pupae in 2013, while these were significantly more abundant in both mixtures compared with the pure stand in 2014. However, their number did not differ significantly between the mixture with and without MeSA. Few ladybirds and lacewings were observed. No significant differences were observed between treatments for parasitoid mummies in 2013. Their abundance was significantly higher in the pure stand of pea compared with both mixtures in 2014. Results from this study show that mixing wheat and pea is an efficient method to maintain aphid populations at a very low level on pea. The use of MeSA did not show significant effects on natural enemies. However, mixing these crops may be enough to reduce aphid populations under an acceptable threshold. [less ▲]

Innovative integrated pest management methods are needed to overcome market withdrawal of synthetic pesticides. Therefore, the identification of environment-friendly bio-products carrying direct or indirect biocide activity is one promising alternative option. Our researches focus on the identification of appropriate formulations releasing volatile organic compounds that are attractant for natural enemies of insect pests. However, the elaboration of slow-release devices that ensure stable and controlled release of active volatile compounds is quite challenging. Here, we developed a formulation based on E-β-farnesene and (-)-β-caryophyllene, these two semiochemicals having strong attractive potential on aphid natural enemies including lady beetles and hoverflies. Both compounds were encapsulated together in alginate gel beads. The blend efficiency was first evaluated through laboratory assays, and then in wheat and broad bean fields, by considering the abundance and diversity of aphids and their natural enemies. [less ▲]

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been ... [more ▼]

Following the introduction of the invasive species Harmonia axyridis (Pallas) in Europe, many research works were conducted on its ecological, economic and social impacts. Recently, our team has been involved in the characterization of the behavioral traits making this lady beetle species so successful. The main conclusions of two PhD works will be shortly presented: (1) Through a six-year inventory performed in Belgian agroecosystems, we have demonstrated that H. axyridis has become well established and was among the most abundant aphidophagous predatory species, causing a severe depression of biodiversity, even if communities of aphid predators are still quite diversified. (2) The social issues associated with the establishment of overwintering aggregations in human constructions were also carefully investigated. We have demonstrated the importance of social interactions on the establishment and cohesion of the aggregates. Finally, we have demonstrated that the deposition of a set of saturated and non-saturated hydrocarbons on the surfaces where the lady beetles were settling on, allowed their conspecifics to follow their markings and join the group. [less ▲]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by ... [more ▼]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by virgin females of the multicolored Asian lady beetle, Harmonia axyridis (Pallas), which were either allowed or not allowed to feed on aphids. Virgin females in the presence of aphids, exhibited “calling behavior”, which is commonly associated with the emission of a sex pheromone in several Coleoptera species. These calling females were found to release a blend of volatile compounds that is involved in the remote attraction (i.e., from a distance) of males. Gas Chromatography Mass Spectrometry (GC-MS) analyses revealed that (–)-β-caryophyllene was the major constituent of the volatile blend (ranging from 80 to 86%), with four other chemical components also being present; β-elemene, methyl-eugenol, α-humulene, and α-bulnesene. In a second set of experiments, the emission of the five constituents identified from the blend was quantified daily over a 9-day period after exposure to aphids. We found that the quantity of all five chemicals significantly increased across the experimental period. Finally, we evaluated the activity of a synthetic blend of these chemicals by performing bioassays which demonstrated the same attractive effect in males only. The results confirm that female H. axyridis produce a volatile sex pheromone. These findings have potential in the development of more specific and efficient biological pest-control management methods aimed at manipulating the behavior of this invasive lady beetle. [less ▲]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by ... [more ▼]

To date, volatile sex pheromones have not been identified in the Coccinellidae family; yet, various studies have suggested that such semiochemicals exist. Here, we collected volatile chemicals released by virgin females of the multicolored Asian lady beetle, Harmonia axyridis (Pallas), which were either allowed or not allowed to feed on aphids. Virgin females in the presence of aphids, exhibited “calling behavior”, which is commonly associated with the emission of a sex pheromone in several Coleoptera species. These calling females were found to release a blend of volatile compounds that is involved in the remote attraction (i.e., from a distance) of males. Gas Chromatography-Mass Spectrometry (GC-MS) analyses revealed that (–)-β-caryophyllene was the major constituent of the volatile blend (ranging from 80 to 86%), with four other chemical components also being present; β-elemene, methyl-eugenol, α-humulene, and α-bulnesene. In a second set of experiments, the emission of the five constituents identified from the blend was quantified daily over a 9-day period after exposure to aphids. We found that the quantity of all five chemicals significantly increased across the experimental period. Finally, we evaluated the activity of a synthetic blend of these chemicals by performing bioassays which demonstrated the same attractive effect in males only. The results confirm that female H. axyridis produce a volatile sex pheromone. These findings have potential in the development of more specific and efficient biological pest-control management methods aimed at manipulating the behavior of this invasive lady beetle. [less ▲]

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native ... [more ▼]

The Multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is one of these species which was intentionally introduced for biological control and has spread from its native range in Central and Eastern Asia to large parts of North and South America, Europe, and Africa. The decline of native species is linked to the spread and the aggressive behaviour of H. axyridis. From 2009, we evaluated the population densities of aphids predator and predator diversities, with a special focus on H. axyridis in agroecosystems of Wallonia (South of Belgium). First, field crops preferences of H. axyridis were determined. Later, changes linked to aphid’s predator populations over time were evaluated. Finally, H. axyridis population changes between two crop farming methods were also evaluated. Samplings performed in agroecosystems highlighted that the community of aphid's predator is composed of few dominant species: three coccinellids (Coccinella septempunctata L., P. quatuordecimpunctata L., and H. axyridis), one syrphid (Episyrphus balteatus De Geer), and one chrysopid (Chrysoperla carnea Stephens). We demonstrated that H. axyridis do not invade all crops at the same rate, maize and broad bean being more infested than wheat and potato at both larval and adult stages. Moreover, H. axyridis populations in maize have strongly increased from 2009 to 2011. Finally, we showed that organic farming do not contribute to increase the abundance of H. axyridis but leads to increase the total abundance of aphid’s natural enemies. [less ▲]

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian ... [more ▼]

Several insect species are known to have different morphotypes, an adaptation to heterogeneities in changing environments. This phenotypic plasticity could be a factor used by the Multicoloured Asian Ladybird, which is considered as an invasive species in Europe since its introduction in the 80’s. Harmonia axyridis has four major morphotypes: 2 melanic forms, conspicua and spectabilis; and 2 non-melanic, succinea and axyridis. In Belgium, only the three first are observed. Literature reports variations in morphotype frequencies, across native and introduced strains. These variations seem to be linked to climate (geographical and seasonal variation), with non-melanic forms being the most abundant in hot and arid climate. This study focused on the variation of morphotype abundance in H. axyridis according to season, field and gender. Adult ladybirds were caught from mid-July to mid-October 2012 into 5 maize fields. The proportions of observed morphotypes were compared according to the sampling season. The abundance of morphotypes was not significantly different through the fields; the observed ratios were 81.6%, 15% and 3.4% for succinea, spectabilis and conspicua respectively. Succinea was the most observed morphotype (χ2=755.8; P<0.001). The total number of collected males and females was the same with ratios of 48.2% and 51.8%: (χ2=0.93; P=0.33). The sex ratio was also not significantly different for each morphotype. There was no evolution of melanic and non-melanic form ratio according to the season, with 25.6% of melanic form in summer and 20.6% in autumn (χ2=1.22; P=0.27). Our results seem to show that morphotype adaptation according to the climate is not observed for Belgian ladybirds. [less ▲]